SULFUR-TRIOXIDE PERMEATION TUBE FOR CALIBRATION OF SULFURIC-ACID MEASUREMENT METHODS

Sulfur trioxide permeation tubes were prepared and calibrated for use in evaluating the effectiveness of flue gas sampling equipment designed for determination of sulfuric acid in fossil fueled combustion sources. By diluting and passing the vapors from the liquid SO3 permeation tube through a midget bubbler, the resulting sulfuric acid aerosol was efficiently collected by a quartz fiber filter and titrated after washing. Over the 45 to 80 °C temperature range, the SO3 permeation rate varied exponentially from about 2 to 35 μL/min with a repeatability of ±8%. At a constant temperature, the repeatability was better than ±3%. The SO3 permeation tube had a projected refrigerated storage lifetime of 30 years, an operating lifetime of 1 month at 65 °C or 1 year at 35 °C, a permeation rate suitable for calibrating H2SO4 flue gas monitors. As a generator for simulating atmospheric H2SO4 aerosol concentrations, a permeation wafer device emitting SO3 at 0.1 μL/min was expected to have a 10-year operating lifetime at 65 °C. © 1979, American Chemical Society. All rights reserved.